A Russian-made Syrian army attack helicopter drops a payload over the rebel-held town of Arbin, in the eastern Ghouta region, on February 20, 2018. #

Smoke rises from the rebel-held besieged town of Hamouriyeh, eastern Ghouta, on February 21, 2018. #

Men walk through rubble after an airstrike in Douma, Syria, on February 7, 2018. #

People are seen inspecting the damage after an air attack in Douma on February 8, 2018. #

A Syrian opposition fighter from the Failaq al-Rahman brigade looks through the scope of a sniper rifle in a damaged building in Arbin on February 15, 2018. #

Syrian opposition fighters from the Failaq al-Rahman brigade communicate to each other from across the rooftops of damaged buildings in Arbin on February 15, 2018. #

A Russian air force Sukhoi Su-34 fighter jet flies above the rebel-held town of Arbin on February 20, 2018. #

Syrian Civil Defense members help an unconscious woman from a shelter in Douma, eastern Ghouta, on February 22, 2018. #

An injured man is seen at a medical station in the besieged town of Douma on February 20, 2018. #

People inspect missile remains in a street in Douma on February 23, 2018. #

Smoke billows following a regime airstrike on the besieged eastern Ghouta region late on February 23, 2018. #

Syrians walk past destroyed buildings in Arbin on February 25, 2018. #

Smoke rises from the besieged eastern Ghouta region on February 27, 2018. #

A Syrian air force Su-17 fighter plane flies over the town of Hamouria on the outskirts of the capital of Damascus on March 3, 2018. #

Smoke and dust rise from part of eastern Ghouta on February 27, 2018. #

Abu Mohammad Alaya, 50, holds a mobile phone with a picture of his son Mohammad, who was killed in Douma on March 2, 2018. #

A man mourns over the body of a boy at a makeshift hospital in Douma following Syrian government bombardments on eastern Ghouta on March 4, 2018. #

Syrians try to identify bodies in a makeshift morgue at a hospital in Douma following Syrian government bombardments on March 4, 2018. #

A scene showing several destroyed buildings in Douma, in the rebel enclave of eastern Ghouta, on March 5, 2018. #

Syrian children stand in a basement being used as a makeshift bomb shelter in the rebel-held town of Douma on March 8, 2018. #

Wounded Syrians await treatment at a clinic in the rebel-held town of Hamouria on March 7, 2018, following reported government bombardments. #

Children gather wood from a downed tree in the street in Douma on March 9, 2018. #

Fire flames rip through a building following a Syrian government bombardment in the town of Douma on March 10, 2018. #

Syrian firefighters use a hose to extinguish a fire following Syrian government shelling on the town of Douma on March 10, 2018. #

People hold a warning leaflet dropped by a plane, entitled "Keep yourself and your family aware," in the besieged town of Douma on March 11, 2018. #

A Syrian child walks down a street past rubble from destroyed buildings in the rebel-held town of Douma on March 8, 2018. #

Smoke billows following a Syrian government bombardment on the rebel-controlled town of Kafr Batna on March 11, 2018. #

A woman gestures as she walks among the rubble and dust of damaged buildings after an airstrike in Douma in eastern Ghouta, Syria, on February 7, 2018. #